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Use of CCSDS Packets Over SpaceWire to Control Hardware

Goddard Space Flight Center, Greenbelt, Maryland

For the Lunar Reconnaissance Orbiter, the Command and Data Handling subsystem consisted of several electronic hardware assemblies that were connected with SpaceWire serial links. Electronic hardware would be commanded/controlled and telemetry data was obtained using the SpaceWire links. Prior art focused on parallel data buses and other types of serial buses, which were not compatible with the SpaceWire and the core flight executive (CFE) software bus.

This innovation applies to anything that utilizes both SpaceWire networks and the CFE software. The CCSDS (Consultative Committee for Space Data Systems) packet contains predetermined values in its payload fields that electronic hardware attached at the terminus of the SpaceWire node would decode, interpret, and execute. The hardware’s interpretation of the packet data would enable the hardware to change its state/configuration (command) or generate status (telemetry). The primary purpose is to provide an interface that is compatible with the hardware and the CFE software bus. By specifying the format of the CCSDS packet, it is possible to specify how the resulting hardware is to be built (in terms of digital logic) that results in a hardware design that can be controlled by the CFE software bus in the final application.

The component parts are the CFE, the electronic hardware attached at the terminus of the SpaceWire link, and the SpaceWire link itself. The CCSDS packet is what is produced by the CFE for control of the hardware as well as obtaining status.

The main benefits of this innovation are the ability to re-use existing CFE flight software code, the hardware responds to “native” CCSDS packets instead of going through a translation layer, and it provides a mechanism to control hardware features using software constructs.

This work was done by Omar Haddad, Michael Blau, Noosha Haghani, William Yuknis, and Dennis Albaijes of Goddard Space Flight Center. GSC-15981-1

Blog: Manufacturing & Prototyping

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